Pressure relief device



April 18, 1939. VON WANGENHEM 2,154,827

PRESSURE RELIEF DEVICE Filed 001;. l'7, 1935 INVENTOR AAJ ATTORNEY Patented Apr. 18, 1939 UNETED STATES ATENT OFFICE PRESSURE RELIEF DEVICE Application October 17, 1935, Serial N0. 45,423

17 Claims.

My invention relates generally to fluid coutaining systems and more particularly to pressure 1elie1 devices therefor.

One of the objects of my invention is 130 pro- 5 vide a pressure re1ief device f the type having a frangible diaphragm adapted to rupture to relieve pressure and t0 provide new anti improved pressure operated mechanism for controlling rupture cf the diapnragm.

Another objec my invention is 130 provide a pressure relief device having a new and improved arrangement of the operating pa1ts thereof.

Another objeci; 01 my Invention is 130 provide a new and improved pressure relief device of the type having a frangible diaphragrn against which pressure acts and to provide a, device of this character which has a, close difierenial benween initial movement of the diaphragm and its relieving point.

'I'he invention consists in the improved construction and combination cf parts to be more fully described hereinafcer and the novelty of which will be particulariy pointed out anc1 dis tinctly claimed.

In the accompanying drawing, to be taken as a part of this specification, I have fully and clearly illustrated my invention, in which drawing Figure 1 is a view shown in cross section of n1y pressure re1ief device;

Fig. 2 is a top plan view taken along the line 22 cf Fig. 1;

Fig. 3 1's a. view shown in cross section haken 5 along the 1ine 3-3 of Fig. l;

Fig. 4 is a bottom plan view of Fig. 1, and

Fig. 5 is a view sin1ilar to Fig. 3 and showing a modified form of my pressure relief device.

Referring to the drawing by characters 01 reference, the numeral I designates a supporting member or Casing which is preferably a casting 0f rectangular form having a bottom wall 2, end Walls 3 and 4, and a side Wall 5. The other side Wal and the top Wall of the casing I are prefera.bly formed by a removable closure member or cover 5 which may be construc'aed of sheet meta1 and be attached to the casing by means of a single screw 1, or be attached in any other suibable manner. In this instance the bottom 50 Wall 2, substantially intermediate end walls 8, I, has an upwardly e.xtending portion or step 8. The step 8 preferably joins and is integral with end Wall 3 anti side Wall 5, and has a Wall 9 fiush with the inner side Wall cf cover 6 and into which the screw 7 may be threaded to attach the cover.

In the portion 8 there is provided a passage or Chamber IQ end leading into chamber IG, through the boutom wall 2, there is an inlet opening or port II which is preferably defined. by a downwardly extending tunular boss I2. A dia-- phragm I3 is provided for closing and sealing the opening 01 passage II, leading into chamber I5, anti a borde1 portion around its periphery seats on the lower end 01" the tubular boss I2. Preferably l1e diaphragm 53 is constructed of a frangible material such as substantially pure tin, tiin being preferable because of its other desirable quaities, namely its non-corrosiveness and its ductility, Ehe latter quality permitting repeated contortions 01 a, slight character of the diapnragm wihoufi its rupturing. Clamping the diaphragm I3 to the boss I 2 obere is a detachable clamping and connecting member I5. 'Ihe clamping member I5 is tubular in form having a passage I5 therethrough which aligns with the diaphragm I3 and opening II. The clamping member I5 has an external fiange I S provided with apertures for receiving screws I'I 'by means of which the diaphragm may be tightly clamped against the end cf b0ss I2.

Preferably the upper end of the clarnping member I5 is recessed, as at I9, for receiving the diaphragm I 3 and also so that the member I5 telescopes over an end portion of the tubular boss I2. 'Ihe upper end of the clamping member I5 is also preferably further recessed, as at 2I'), the 1ecess 25 preferably being concentric with diaphragm I3 with the inner side Wall defining the recess 20 being of lass diameter than the opening II. Thus an inner border portion of recessed Wall I9, around its entire periphery, provides an upwardly facing shoulder or seating surface 22, the purpose of Which is hereafter described. 'I11e tubular clarnping member I5 may be internally threaded for connection in a fluid line or to a fluid containing receptacle such as a heiler, the pressure of Ehe fiuid thus acting againsz'; the frangible dia.phragrn I3. Leading out cf chamber I I3 the're is an outlet passage 24 through end Wall 3 and preferably the passage 24 is defineci by an externally exending tubular boss 25 formed inegral With Wall 3. The tubular boss 25 may be internally threaded for sonnent1'on With a drein 01 return line, as desired.

Disposed in chamber I!) there is a movable backing member for the diaphragm I3 and which includes a plate-like member 25 which normally seats an the annular shoulder 22. The lower face of the plate member 26 thus engages the upper side of the diaphragm I 3 and preferably the plate 26 is circular in form and has a sliding fit With the inner side Wall defining the opening I l. It will thus be appareni: that the p1ate rnem her 26 also serves as a valve disc, closing the opening H ancl on1y permitting fu11 egress of fluid into chamber III upon movement or" mernber 26 completely out 01: portor aperture II. The diaphragm I3, constructed of non-corrosive material and. disposed between the va1ve member 26 and the fluid, prevents the va1ve member from corroding and thus eliminates sticking of the valve member whion would otherwise 000111. The backing mernber, er valve, also incluo'les a stem portion 2i which is rigidly fixed at one end to the p1ate 25 and extencls upwardly therefrom. The stem 27 extends through an aperture in the stepped Wall 8 and is guid.ed therein, an upper portion of the stem 2? extencling above the upper face of the stepped Wall 8. Preferably the valve member or plate 2%, as wel1 as its stem 21, is guided in its rnovement to insure its proper alignment With valve port II and 110 insure its free movernent therein. In ehe present instance, the member 26 is guided by a plurality of vertically extending ribs 28 formed on the inner Wall of chamber ID and extending from the bottom Wall of the casing substantially 130 the inner face of the Wall or ssep 8. Ehe ribs 28 may be arranged in spaced relation surrounding the valve member 2.5, With their inwardly extending faces preierably being shaped 110 conforrn to the unter sontour of memoer 2B.

In order to provide an efiicient pressure relief devioe ancl one which has a close rlifierential between initial movement of the diaphragm and its relieving point, I provide pressure aotuated mechanism Whih includes a foroe transmitting means in th-e form of a 1ever 36. The lever 38 is fulcrurned within the casing I and is disposed immediately above the upper end of the soem 21. The 1ever 3i is preferaloly consaructed of flat, plate-like material or sheet metal and is arranged so that its lower edge normally bears on the upper end of the stem 2I, the upper end of the stem preferably being rounded to reduce friotion between the parts. The lever 30 preferably extends substantially from end Wall 3 to end Wall 4 in order to obtain good leverage, Supported in the stepped wal1 8, between the end Wall 3 and stem 2'I, obere is a removable supporting rnember 3| 130 Which one enol of the lever 30 is pivoted, the supporting mernber preferably being located intermediate the side Wall 5 and Ehe side Wall of cover 6. The supporting member 3l is preferably disposed acljac-ent the stem 27 so as to obtain a relatively s'nort lever arm between the supporting member anti stern, as comparecl to the lever arm etween the stem and Ehe other end of the lever. The supporting member 3I preferably has its upper end portion bifurcated so receive the lever, the lever and bifurcated end of the supporting mernber being provided. with aligning apertures 130 receive a pin 32. The supporting member 3l is also free1y rotatable and preferably its lower end portion is threaded for screw-threading into the stepped Wall 8, che threaded engagement, however, being sufficiently free or 1oose 130 permit substantially frictionless swiveling of the member 3I.

T establish the pressure at Whic-h the frangib1e diaphragm is to be permitted to rupture, and at Whioh the valve or backing member 26 is to be moved out of port l I to relieve the pressure in inlet I6, I provide spring means 33 for exerting a force, through I;he lever and against tne valve or backing member for opposing rupture of the diaphragm and rnovement of the valve member by forces less than the force exerted by the spring means. In the present instance, the spring means oonsists of a single spring, preferably of the ooi1 or ne1ical type, the spring being disposed in the casing a1; one sicle of the diaphragm anal backing member. The spring 33 has one end connected to the lever 35, preferably at a point adjaoent Ehe free end of the lever so as tohave a reiatively long lever arm from ehe point of attachment of the spring to the lever, to the point of engagernent of the lever and. the stem 21I. The lower end of spring 33 is preferably anchored to the bottom Wall 2 of the casing, and preferably the lower end of the spring is attached to an adjustable member or pin 34 so that the tension of 1;he spring, and therefore the pressure at which the diaphragm will rupture, can be varied. The bottom Wall 2 is provided. Wi'n an aperture there through for receiving tne pin S E, the aperture having a bore of sufficiently large diameter to sliolably receive the pin. The lower enol of the pin 3d projects externally of the casing and is threadeci to receive an adjustment er stop nut 35, whioh nut abuts the unclersio'le of the bottom wall 2 to hold the spring 33 under tension. Freierab1y the nut 35 is providec'l WiCh a number of aper'ures and the pin 3 is provided With a slot for receiving a cotter pin, or the like, 130 prevent rooation of the nub relative to pin 35 after spring 33 is placed under the desired tension. Freierably the spring 33 is anohored to the bottom wall 2 ab a point adjacent the sicle Wall of cover 6 so that the lever is actecl upon by components of the spring foroe, ior a purpose to be hereafter describeol.

Integral with the enol Wall 3 and. side Wall 5, and. disposed at the juncion or in the oorner formed by these Wa1ls, there is a boss 3% which extends into the casing for supporting an adjustable stop or latch member 3'I which is preferably a screw or threaded pin. The boss 3*3 is disposed intermediate I;he top anol bottom Wall of the casing and has a vertically extending threaded bore whioh opens through its upper and lower ends and in Which the sorew 37 is threacled. In the bottorin Wall 2 there is provided an aperture 38 Which registers with tl1e threaded bare und. threaded pin 31 is provided in its lower end, with a slot for receiving a tool which may be inserted through aperture 33 for adjusting the vertical position of the stop pin 3'I. As is more clearly shown in Fig. 2, when the devioe is sei; for operation the lever 39 is disposed at an angle to the side Wall 5, With its free end extenoling between side Wall and the stop pin 3'fi, 'nhe lever being hold against Ehe pin 37 loy spring 33. Extencling through the sicle wall 4 there is a bore 33 which intersects the bore of pin 3'I, the bore 38 being provideol to receive a looking sorew 39 for preventing rotation of stop pin 37 after it is set. Between I;he inner enol of screw EI9 and the stop pin 3'I there is preferably provided a pieoe of soft metallic material such as lead, indioated at 4G, for frictional engagemenn With screw 39 so that the threads thereof Will not be injured. As shown in Fig. l, the stop screw 3? is preferably set so that only a small portion of its upper end extends above the lower edge of the lever 3i3.

As shown in Fig. 3, the spring 33 is disposed ab an angle relative to the verbical and horizontal planeg in which the 1ever 35 is adapted 130 move. The spring 33 thus exerts a force having two componenus, the veri;ioal component of the force tending to pivot lever 30 downwardiy and the horizontal component tending to swivel the lever in a horizontal plane. As shown in Fig. 2, the spring 33 is also preferably disposed With its longitudinal centerline substantiaily defining a chord of a circle having pin 3! as its center so as to get maximum throw or swing of lever 30 upon its release.

The operation of my pressure relief device is as foilows: The pressure at which the clevice Will operate to relieve the pressure is determined by the force exerted by spring 33, opposing movement of valve member 26, and by the position of the upper end of the adjustable latch memher 37 with respect to the lower edge of the lever 33. When the force acting against the frangible diaphragrn 13 and the movable backing plate, or valve 26, exceeds the opposing force exerteai by the spring '33, the va1ve member 25 begins t0 move upwarclly or away from its seat 22. Upward mevement cf the valve member 28 is transmittecl to the lever 30 by the stem 27 and if the upward movement is suificient so that the free end of the lever is raised above the upper end of the latch member 3'!, then the horizontal component of the spring force becomes effective t0 pivot or svrivel the lever 30 in a horizontal plane. After the lever 30 is moved horizontaliy a precletermined distance, it moves out cf aligning engagernent with the valve stem 21 and When this occurs the valve member will be instantly thrust upwarcily by the fluid pressure, which pressure wil1 of course, rupture the frangible diaphragm. The pressure is thus relievecl and the fluid rnay pass through chamber 50 and. Gut of the outlet 24 thereof. After operation of the device, the clamping member E5 may be readily removed. and a new diaphragm inserted in its recessecl wal1 anal be clamped in place by the screws i l. The pressure actuated mechanism 01" the device is then reset by svvinging the free end 0f lever 30 over to its latch 31 and raising the free enel of the lever t0 position it on the opposite side o1" lat-ch 3T. The spring 33 is thus placed. under tension and hold.s the lever 30 against the latch 3T.

By provicling a force transmitting means such the lever 30, and arranging the same so that it wiii be actuated to disengage from the va1ve at a precleterrninecl pressure, it Will be seen that the opposing force of the spring 33 is rendered. instantly and entirely ineffective in opposing movement 0f the va1ve member when such disengagement occurs. As a result, the valve metaber is free to be moved away from its seat by the fiuicl pressure to instantly open the valve port t0 its maximum capacity for relieving the pressure. Also, by providing the lever 30 With a relatively short lever arm from its fulcrum to the valve stem as compared t0 the length of the lever arm from the stem 27 to the latch 37, it will be understood that slight upward movement cf stem 27 will result in the free end of the lever being moved through a relatively large arc. As a result, relatively small movement of the valve Will be suflicient to cause the lever 30 to be disengaged from the valve stem 2'! and because 01 this, the device can be set to safeiy operate at a pressure relativeiy close to the predetermined danger pressure. This prevents unnecessary Operation cf the pressure relief clevice at pressures Which approach, but do not reach, the danger pressure and which may be caused. by so-called hamrner knock.

T0 construct a practicai and satisfactory de- .0035 of an inch before the free end of the lever is movecl .020 of an inch or becomes unlatched. The above figures provide for approximately a five pounci pressure increase between initial movement cf the vaive and unlatching of the lever. If ciesirezi, or found necessary under certain con-* ditions, the latch 37 may be raised, for example, so that its upper end extends .040 of an inch abnve the iower edge 01 the lever when in latched position. In th1's position of the latch the preseure, i1 xrease between the initial movement of the valve and the point at Which the lever becomes unlatched, Will be about ten pounds pressure. Because of the ductility of the diaphragm 53 and. the arrangement whereby the lever 30 and valVe become ciisengaged, it Will be seen that the diaphragm Wiil not rupture until substantialiy ehe exact pressure has been reached for Whiell the device is set to operate. That is to say, although there may be slight mo vement of the vaive at pressures approximating the operatpressure, the lever 30 Will not be swung out of gement Wit-li the stem 27 untii its free end has WO spr1ngs 40 and 39 are employed, instead er a singie spring. The spring 40 is arranged with its longitudinal axis vertically disposeci and nas 0ne end connecwecl t0 the lever 30 and the other anchored t0 the bottom Wall 2 cf the cas- The spring 00 thus acts solely to oppose movcment of the vaive member. The spring 4l is arre ed With its longitudinal axis horizontally (lisp and the etl1er end anchored. to the side Wall 5 of the casing, Th spring 31 thus acts solely meve the lever 30 out of engagement with the valve stem 2l' when the free end cf the lever is n1oa eci. abave the latcl1 3i'. 4

What I claim and desire to secure by Letters Patent of the United States is:

1. A pressure relief device comprising a supporting member having an opening therein, a frangible diaphragm held at its periphery to saicl' supporting member and sealing said opening, said ciiaphragm beiz1g exposed to pressure acting 011 one side thereof, a backing member disposeci on the other side 01" said diaphragm and movable relative thereto, a iever member normally engaging said. backing member, a single spring exerting a force acting through saiol lever member to oppose'movernent cf saicl baci :ing member and also acting upun predetermined movement there cf to disengage saiol lever member from saidj backing rnember so that the frangible diaphragm can rupture t relieve the pressure, and iatch means cooperable With seid lever member to prevent disengagement of said lever member and saiol backing member at pressures below a pre= Also, the latch may be adjusted -secl with one end connected t0 the lever 30 movable backing member for said. diaphragm ancl disposed 011 the other sicle thereof, a lever member normally engaging saic'l backing member and movalole for disengagement therefrom, spring means acting through said lever member to oppose movement of said backing member and. also acting upon precletermined movement o1? saicl backing member by saicl pressure to move said lever member out of engagement therewith so that said diaphragm can rupture to relieve Ehe pressure, ancl latoh means acting to prevent disengagement of said. lever memloer and. saicl backing rnemloer at pressures below a redetermined pressure.

3. In a pressure relief device for relieving pressure in a fiuicl receptacle having an opening therein, a frangible diapnragm sealing saicl opening anal against one sicle of whlch pressure acts, a movable backing member for saicl diaphragm anal cllsposed on the other sicle thereof, sald baclzing member being movable relative to saicl diaphragm a lever engaglng said backing meznloer, said. lever havlng a fulcrum ancl being movable about its fulcrum to urge saicl b-acking member toward said dlapnragm, saicl lever also being laterally movalole for disengagement from said backing member so that saicl diaphragm Will ruptnre to relieve the pressure, sprin means actlng through said lever to oppose movsment 01 seid member also acting to move said lever out of engagement With saicl backing mernber, and means preventing lateral movemen-t of lever at pressures belovv a preoleterminecl pressure.

4. In a pressure relief device having a passage sealed by a frangible diaphragm and a movable backing member therefor, a lever member normally engaging said backing member for urglng the latter toward said diaphragm, said lever member being fulcrumed for mcvernent in the cllrection of movement of said backing member ancl also being movable laterally thereto for disen gagement from saicl backing member, a coll spring exerting a force on said lever member and acting to oppose movernent of salcl bacl ing memloer and also acting to move said lever mernber out of engagement with sald backing member, and means preventing lateral movement of saicl lever men1b-er at pressures below a predetermined pressure.

5. A p-zessure rellef deviee cornnrising a casing having a passage therethrough, a frangible diaphragm sealing said passage and against on-e sicle 0f whicn pressure aots, a movalole backing rnember for sald cllaphragm anol disposed 011 the other side thereof, yieldable means disposecl in saicl casing exteriorly of salcl passage, saicl yieldalole means belng disposed at one sicle of saicl diaphragm and exerting a force opposing movement of said backing member, movable connecting means operatlvely connecting salcl yieldable means and said backlng memoer anal movalole by said ylelclable means upon oocurrence of a predetermined pressure for disconnecting saicl backing member ancl said yieldable means w'nere by said diaphragm will rupture to relieve the pressure, and means for preventing disengagernent 0f said baoklng member and said connecting means at pressures below a predetelminecl pressure.

6. A pressure relief clevlce comprising a casing having a passage therein, a frangilole dlaphragrn closing and sealing said. passage and against one side of which pressure aots a mova'ole backing member for the cliaphragm anti disposeol on tl1e other side thereof, said backing member having a stem member extending upwardly therefrom, a lever fulcrumed in saiol casing and normally engaging the upper end of said stem, saicl lever beingmovaele laterally to and out of engagement with saiol st-em so that the backing member can move anal tine diapnragm rupture t0 relieve the pressure, means exerting a force through said lever to arge saicl backing plate downwardly against naovement by the fluld pressure and also actlng to move salcl lever out 0I" engagement with sa:id si:em upon predetermined upward movement of sa7l. lever by the pressure, and stop means cooperable With said laver to prevent lateral movernent cf said lever at pressures below a predetermined pressure.

'Z. A pressure relief devlce comprising a casing having a passage therethrough, a frangible diaplzragrn sealing said passage ancl against one side 01 wl1ion pressure acts, a movable backing mer for saio. cllaphragm and disposed. on the other side thereof, a lever member engaging baol;ing rnember, said. lever member being movable in the direction of movement of said backing mernloer anal also being movalole laterally to for disengagement from said backing m:.'gu.'l er, a -soll spring disposed With its longituclinal axis angularly disposed relative to the "planes ol' movernent of said lever member Wherea co2z;ponent o1 the spring force acts to move =a,id ievor member against saicl backing member ano-s'ner comnonent 01 the force acts to move "vs. ne' u;l out of engagement With said morn'eer, anal stop means engaglng' said l aber to prevent lateral movement theret pressures below a predetermined pressure.

8. ressure relief device comprlsing a casing a therein for fluicl, a movable valve mernber lor closing salol passage and agalnst one sie o1" Whioh tne fluicl pres-sure acts, a frangible eliaphragm of non-corrosive material disposecl between saicl one side of salcl valve member and the fluicl to prevent corrodlng 03 saicl valve membar, saicl frangilole clapnragm being reenforce oy saicl valve memeer, a lever mernber normally enng sald. valve meznber ancl being movalole for disongagement from saiol valve member, yield able lneans acting through sarld lever member for opposlng movement 02 said valve member, means operable upon increase in pressure to a predetermined pressnre for moving said lever mernber 110 disengage the same from saicl valve memloer, ancl latch means lor preventing movement of said lever memoer loy saicl lastnamed means at pressnres below a precletermined pressure.

9. A pressure reliel devlce comprising a casing having a passage therein 3Tor the passage 01" fluid, a movable valve member for closing said passage against one side of whioh the fiuid pressure ets, a lever me1nber fulcrumecl in saicl casing anal normally engaging said valve member, means exerting a foree acting througn said lever mentber to hohl ;aicl valve member in closecl position, saicl lever *mloer also beim; supporte to swivel anal disengage frem said valve mernber to render saiol foree inefiecve, 1ne-ans Ior moving said. lever memb r 1or disengagement from sald. valve mem ber upon inorease in pressure acting the1eagainst to a precletermlneol pressure, anal means for pre- Venting, swivel movement of saicl 1ever member at pressures belovv a predetermined pressure.

19. In a nressure relief device, a supporting mewloer having an opening thereinamovable closure rnember for closing sai d opening and against Whi h fiuid pressure acts tnding to move said closure member to an open position, a lever member having operative connection with said closure member for transmitting a force to hold said closure member in closed position, said lever member being fulcrumed for pivotal movement in the direction of movement of said closure member and also being pivotal in a lateral direction relative to said closure member so that said closure member can move to said open position, yieldable means acting through said lever member to hold said closure member in closed position and also acting to move said lever member in said lateral direction, and stop means cooperable With said lever member to prevent lateral movement of said lever member at pressures below a predetermined pressure.

11. In a pressure relief device, a supporting member having an op8ning therein, a movable closure member for closing said opening and against which fluid pressure acts to move said closure member to an open position, a lever membei for transmitting a force to hold said closure member in closed position and mounted for pivotal movement in substantially the same direction as the direction of movement of said closure member, said lever member also being mounted to swivel in a direction substantially lateral to the direction of movement of said closure member to move out of holding relation with said closure member, a stop member fixecl relative to said lever member for preventing swivel movement of said lever member at pressures below a predetermi'ned pressure, said stop member normally engaging said lever member With disengagement therebetween being eifected upon pivotal movement of said level member in one direotion through a predetermined angle, and yieldable means opposing pivotal movement of said lever member in said one direction and. acting through said lever member to hold said closure member in closed position, said yieldable means also being operable to swivel said lever member upon movement of said lever member through said predetermined angle.

12. In a pressure relief device, a supporting member having an opening therein, a movable closure member for closing said opening and against which fiuid pressure acts to move said closure member to an open position, a lever member for transmitting a force to hold said closure member in closed position and mounted for pivotal movement in substantially the same direction as the direction of movement of said closure member, said lever member also being mounted to swivel in a direction substantially lateral to the direction of movement of said closure member t-o move out of holding relation With said closure member, a stop member ior preventing swivel movement of said lever member at pressures below a predetermined. pressure, said stop member normally engaging said lever member with disengagement therebetween being effected upon pivotal movement of said lever member in one direction through a predetermined angle, and a spring under tension having one end attached to said lever member and acting t0 pivot said lever member in the opposite direction to hold said closure member in closed position and also acting to swivel said lever member.

13. A pressure relief device comprising, means having an opening for relief of pressure, a movable closure member for said opening and against Which pressure acts to move said closure member to an open position, movable force transmitting means engageable with said closure member and being movable out of engagement therewith, a

single spring exerting a force acting on said force transmitting means to hold said closure member in closed position, said spring also being operable to move said force transmitting means out of holding engagement with said closure member so that said closure member can move to an open position, and means restraining movement of said force transmitting means by said spring out of holding engagement with said closure member at pressures below a predetermined pressure acting against said closure member.

14. A pressure relief device comprising, a wall having an opening for relief of pressure, a mov able closure member for closing saidopening, a lever member to transmit a force to hold said closure member in closecl position and fulcrumed to pivot in the direction of movement of said closure member, said lever member also being arranged to sWivel relative to and out of holding relation with said closure member, yieldable means exerting a force acting through said lever member to hold said closure member in closed position, yieldable means exerting a force acting to swivel said lever member, and means to prevent swivel movement of said lever member at pressures below a predetermined pressure.

15. In a device of the character described, a casing having a pressure chamber, a pressure operated member movable by pressure in said chamber, an arm member secured at one end to said casing and having a portion abutting said pressure operated member, said arm member portion being laterally movable out of abutment With said pressure operated member, means acting on said arm member and exerting a force to move said arm member laterally and also to hold. said arm member portion in abutment with said pressure operatecl member, and means opposing lateral movement of said arm member.

16. In a device of the oharaeter described, a pressure chamber, means movable by pressure in said chamber, swingable means in the path of movement of said means and movable therefrom, means acting to move said second means out of said path and determining the pressure in said chamber to move said first means, and means holding said second means in said path for a. predetermined extent of movement of said first means.

17. In a relief valve of the character described, a oasing having a passageway therethrough inoluding a valve port, frangible means olosing said port to flow of fluid, means reenforcing said frangible means and movable relative thereto,

fulcrum means secured to said casing and rotatable in a plane parallel to the plane of said port, lever means rotatably secured to said fulcrum means for movement in a plane perpendicular the plane of said port, said lever means being operable to llrge said reenforcing means toward reenforcing position and being movable with said fulcrum means to release said reenforcing means, means having a force oomponent toarge said fulcrum means in its rotational movement and hav1'ng a second force component to urge said lever means in its rotational movement to urge said reenforcing means toward said position, means limiting movement of said reenforcing means toward said position, and means cooperating with said fulcrum means to limit releasing rotat1'on of said fulcrum means to maintain said reenforoing means in reenforcing position below a predetermined pressure in said passageway acting against said frangible means.

ADOLF von WANGENHEIM. 

